Grinding wheel spindle



Oct. 30, 1934.

P. DAVEY GRINDING WHEEL SPINDLE Filed May 3, 1952 INVENTOR- BY I KW Patented Oct. 30, 1934 1:: 1 JUNITED STATES PATENT OFFICE GRINDING WHEEL SPINDLE Peter Davey, Mount Vernon, N. Y.

Application May 3, 1932, Serial No. 609,003

3 Claims.

This invention relates to grinding machines, more especially to machines for precision grinding of metallic bodies, and more particularly to the grinding wheel spindle thereof.

It is well understood that many parts of modern' machinery, :especially relatively moving parts, are finished by a grinding operation which is designed to bring the part to the precise form and dimensions desired. Machines for performing this grinding, are truly machines of the utmost precision, andthey produce an article of substantially the perfection desired within the fixed tolerance limits.

It has been found, however, that such precision grinding machines, especially those used for producing the internal surface of a race, either ball or roller, at times produce such articles which, although substantially perfect, nevertheless, exhibit a multitude of extremely slight microscopic valleys and ridges called, chatter marks, n theground surface. The effect of these chatter marks is observable when the ground article is put into use, causing an undesired vibration of the associated parts which becomes accentuated by further use.

Many attempts have been made to obviate the production of these undesired chatter marks. When they occur in a product, some believe that further occurrence thereof may be prevented by changing the abrasive or' grinding wheel, others change the wheel spindle, either substituting another spindle of exactly the same form and size or another spindle slightly different in some respect. Many theories of the cause of this difficulty have been evolved, and depending upon the particular theory believed, one or the other of the theoretical remedies is applied, but with no uniform success because, apparently, the true reason for the formation is not known.

I have made an extensive study of the problem of preventing such chatter marks, and have made numerous experiments to determine the cause thereof. My extensive study and experiments, involving the use of different grades and sizes of grinding wheels, different sizes and designs of grinding wheel spindles, and relative speeds of the work operated upon and the grinding wheel itself, have disclosed to me that, contrary to prevailing opinion, the chatter marks in question, are not always caused by an unbalance either in the grinding wheel or the spindle or its associated parts, but the formation of the chatter marks is due to what might be called substantially instantaneous changes in speed of relative rotation between the grinding wheel and the article operated upon. This relative change, I have ascertained, is usually due to a momentary slight relative twisting back and forth, of parts of the spindle carrying the grinding Wheel.

Guided by my investigations and discoveries, my principal object is to produce a construction of grinding wheel spindle and associated parts which will obviate the objectionable difficulty hereinbefore mentioned.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses, and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawing and the several views thereon, in which like characters of reference designate like parts throughout the several views, and in which:

Figure 1 is a sectional view of a grinding spindle and its bearin'gs; Fig. 2 is a top plan view of the device as shown by Fig. 1, with certain parts in section to more clearly show the construction and with a grinding wheel attached to the spindle of the device.

In order to illustrate and describe the principle underlying my invention and the best construction of a device embodying my invention, I have illustrated, in the drawing a simple grinding machine with my invention incorporated therein.

The fragmentary grinding machine illustrated by me in the drawing is, in parts, of conventional arrangement. A grinding wheel 1, shown in Fig. 2, is mounted on a spindle 2. This spindle is continuous from the left to the right hand end, as shown in Fig. 1. The spindle is supported by ball races 3 which in turn are supported by the balls 4, race 5 and support 6, fastened or secured in any appropriate manner to a stationary support as 7.

The spindle 2 extends to the right, as shown in Fig. l and supports ball races 8 which, through the balls 9 and races 10, support the pulley or driver 11 about which passes driving belt 12 from the source of power.

Ordinarily the pulley or driver 11 does not rotate independently of the spindle 2, but is fastened rigidly to the spindle 2. In applicants construction, however, the driver or pulley is not fastened in the usual manner rigidly to the spindle. Applicant attaches a shouldered v1.10

construction anything which causes, in effect, a I more than or less than normal speed of thedriver 11, that is, an accelerationor decelera-- tion, is not transmitted directly to the spindle 2, but being transmitted to the spring 16; causesa tightening or loosening ofithespring The tightening or loosening of" the spring tends to set up an oscillation in the spring which:

is in the direction of the first oscillation, opposite to that-in which the" spring is moved bythea'cceleratin'g or decelerating force. This oscillation of the spring and the energy ofthe acceleration or deceleration is absorbed or dissipated by a friction damper. This damper in dissipating the energy of an accelerating or decelerating force also tends to reduce" the amplitude of the oscillation'of thespring:

In order to prevent this oscillation as much as can conveniently be done, applicant employs a damper or brake; which in the form-shown for" illustration comprises a resilient spring member 22' having on each'enda pad or shoe member, as 23 and 24, bearing against the thimble casing 21" which is attached to the driver 111 This spring-member 22'is attached to the spindle 2' by means of thescrew 25 which may beadjustedin or'out so-astoincrease or decrease the frictiona'l engagement between the thimble casing-21' and the pads 23 and 24. Apreferred adjustment' of this damper'or brake is such that the oscillations of the spring 16 arereduced'to a minimum without at the same time introducing's'o-much friction between the sleve-21 and thepads23 as tonullify the effect of'the spring 165 Thus'by absorbing the accelerating or decelerating forcein' the spring, l6and' then-dissipating the energythereof by means of the damper 22 rapidchan'ges in speed of 'the'grindin'g-wheel in relation to-thework being ground is'prevented and the objectionable chatter marks on" the surface-of" the work" being ground are not formed.

In order to prevent an unbalance applicant has placed a dummy screw and collar 19 on the side of the sleeve opposite 1'7 and has placed a dummy sleeve and collar 20 on the spindle opposite the screw 18.

In order to protect the resilient means 16 applicant covers the same with a thimble casing 21.

Although I have particularly described one particular embodiment of my invention and explained *the principle and T construction thereof, nevertheless, I desire to have it understood that the form selected is merely illustrative, but does not exhaust the possible physical embodiments of the ideaof means underlying my invention.

Wliatfclaim as new and desire to secure by LettersuRiitentiof the United States, is:

l. Ina grindingmachine, in combination: a grinding wheel; a rotatable spindle upon which the wheel is rigidly mounted; fixed bearings in which the spindle is mounted; a rotatable driver for thespindle adapted to be. rotated from' a source of power; means interposed. between the driver and the spindlezadapted'toitransmit rotative force from the.driverltoith'eispindle *andnto allow some rotational movement between the driverand theispindle. andtmeans :acting .to prevent *too rapid' recoveryi of a: former: relative rotational position after departure therefrom.

2. Inai'grinding machine; .in combinationr'a grinding wheel; a rotatable spindle upon: which the wheel. is rigidlvmounted; fixed bearings in which the spindle is mounted; a rotatable driver for the spindle adapted to: be'zrotatedpfrom a source-of power; resilient means interposed between the driver and thesspindle' adapted to transmit rotative force from the: driver to the spindlefand to allow some: rotational movement in either directionbetween.therdriver and the spindle-at all timesiduringthe rotation of the spindle; andimeans acting to prevent too rapid recovery ofia former relative rotationalposition after a departure therefrom.

3'; Inga grindingmachine, in combination: a grinding-wheel; a rotatable spindle upon which the Wheel is rigidly mounted; ia fixed'bearing in which the spindle isimounted'; a driver mounted on the spindle and rotatable thereabout; said driver having ani extended sleeve enclosing a portion of the spindle attached thereto; a helical spring wrapped-about theisleeve. and having one end attached to the sleeve and the other: en attached to the spindle.

PETER DAVEY. 

